1. Significant Figures

2. Uncertainty We do not know infinite digits of a measurement
Exact numbers are known for sure
Inexact – have some question (estimates)

3. Precision and Accuracy
Accuracy refers to the agreement of a particular value with the true value.
Precision refers to the degree of agreement among several measurements made in the same manner.
Precise but not accurate
Neither accurate nor precise
Precise AND accurate

4. Reporting Numbers
When reading an instrument, all exact decimal places should be read – these are numbers actually represented by lines on the instrument
In addition to the exact numbers, one inexact decimal place should also be estimated – this is a digit in between the smallest lines
All digits including the uncertain one are called significant figures
We are fairly confident of these digits

5. Which Digits Are Significant?
Any non-zero number is significant
Any number to the left of a decimal is significant
Zeros to the right of a decimal and behind other numbers are significant
Zeros to the right of a decimal but in front of other numbers are not significant

6. How many Significant Figures in each below?
) 3440. ) )
) 1002
) 400. )
) 6000 )

7. Round each to 3 Significant Figures)
) 6.561 ) ) )

8. Percent Error Mathematical measure of accuracy
Tells how far a measurement varies from the actual value
Actual Value – Measured Value
X 100
% Error =
Actual Value